Treatment of wood-pulp.



B. T. NASE.

TREATMENT OF WOOD PULP.

APPLICATION rum) 11110. 2, 1911.

1 0 1 316 Patented May13,1913.

- cooking operation,

separate the UNITED STATES PATENT OFFICE.

nAmvAnAs 7r. NAsn; or SAN FRANCISCO, cALIronNIA, Assieivon 'ro STANLEYPAPER cAmroammA coaronA'rrou or AmzonA.

FIBER co.,,or SAN FRANCISCO,

i TREATMENT OF WOOD-PULP.

Patented Ma 13,1913.

Application filed December 2, 1911. Serial No. 663,488.

Tb all whom it may concern:

Be itknown that I, BARNABAS T. NAsn, a subject of the 'King'of GreatBritain, residing in the city and county of San Francisco and State ofCalifornia, have invented new and useful Improvements in Treatment ofWood-Pulp, of which the following is a specification.

This invention relates to the treatment of wood pulp for use in papermanufacture, and pertains particularly to a method of, and means for,the removing and recovering of soda Values of the caustic soda used indigesting the pulp.

It is the object of this invention to provide a simple and effectiveprocess for treating digested fibrous materials to removechemical-containing liqu rs therefrom so that the digested fibrousmaterial or pulp will be practically freed from the chemicals employedor liberated in the digesting process, and the digesting chemicalsrestored for reuse.

Another object is to provide a process of the above character which ishighly efiective, and by the employment of which, the desired resultsmay be obtained with greater rapidity and effectiveness than is possiblein the processes now generally used.

In the manufacture of wood pulp, in which the process constituting mypresent invention is employed, the wood or other fibrous material to beconverted into pulp is cut into short lengths and bogged to fibers, sothat they will be thoroughly acted on in the cooking rocess.

. The fibrous material is then subjects to the cooking operation, which,in brief, consists of subjecting it in a closed cooking tank or digesterto a solution of caustic soda, and then cooking it for a period ofapproximately ten hours, by means of steam, under a pressure ranging upto 120 pounds to the square inch and at a temperature of approximately320 F.

When the cooking of the fibers in the soda solution has beenaccomplished, the "cooked fibers and the liquors in the digester aredischarged therefrom, and are then so treated as to remove the liquor,comprising the caustic soda solution and such chemicals as may becomeincorporated therewith in the from the fibrous mass. This is done withthe object of freeing the fibrous mass or pulp from the caustic sodasolution, or digesting liquor, preparatory to using the pulp in themanufacture of paper or other'articles.v

The purpose of the present invention, as before mentioned, is tothoroughly remove the chemical containing, digesting liquor from thefibrous pulp after the cooking process just described. Heretofore thishas usually been accomplished by discharging the cooked mixture from thedigester, under 120 pounds pressure per square inch, into a receivintank having a series of bafile plates for brea ing u the cells and dis'te atin the fibrous ma s. The chemical ionfiinin liquors are thendrained from the tank an delivered to an evaporating plant. The drainedpulp is put into washing tanks, where it is agitated in washwater,'which is drawn off and delivered to the evaporatin plant, whereit is mixed with the chemica containing liquors previously separatedfrom the pulp. The liquor being concentrated in the evaporator is thendelivered to an open incinerating plant, which acts to convert solidresidue into ash, from which the soda is leached with water. Thecarbonate of .soda thus obtained is then treated with lime to convert itinto caustic soda, the recovery of which is about 80% of the causticsoda employed in the original soda solution used in the digester.

In the old process just described a large quantity of water is used inthe washing operation, which is objectionable, inasmuch as considerabletime and fuel is required in evaporation and condensing it in theevaporatin plant. after eing washed, is put through a series of screensto separate the non-digested or coarse portions of the fiber, which aredried and burned in a furnace, thus entailing an objectionable wastewhich my present process eliminates.

The apparatus-employed in carrying out my invention is shown in theaccompanying drawing, in which the figure is a'diagrammatic view showingthe apparatus partly in elevation and partly in section.

In the drawing, A indicates a digester of any suitable description,having a gated discharge opening at its lower end, through which thecontents of the digester, consisting of the cooked fibers and thedigesting liquor, may be discharged into a receiving hopper 2.

In this old process, the pulp,

An endless conveyer belt 3 leads beneath the discharge opening 4 of thehopper 2,

onto. which the digested mixture is fed; a

gate 5 over the opening 4 being employed for regulating the flow of themixture onto the belt 3. From the belt 3 the mass is deliveredto a chute6 and is discharged between 21. pair of horizontally extendingsuperposed rollers 77, which are corrugated compressed and disintegratedfibrous mass is discharged onto a conveye'r belt 10, after leaving therollers 7 -7, and after belng subjected to a Washing spray 13, fromwhence it is fed between a second pair of rollers l1-11, correspondingto the rollers 7-7, where it is subjected toa second com-u pressingaction, then to a second washing by spray l3' and delivered to aconveyer belt 12, from whence it is discharged to any desired mechanism.

The fibrous mass, on leaving the rollers 77', is largely free from thedigesting liquor and is in a high state of compression. A stream ofclear, preferably warm, water in fine jets is discharged from the pipe13 upon the fibers the moment they pass through the rollers 77. andbegln to expand; the Water discharged upon the fibrous mass being ofsuch quantityonly as the fibers are capable of absorbing and holding, sothat practically no water will flow into the pan 9 at this point.

The washing of the pulp goods by the spray 13 on leaving rollers 1111.is of the same character; care in each case being' taken to spray thefibers to a point only short of saturation, so that by the firstspraying the chemical solution collected in tank 9 and the ultimatefiber product which is delivered by the conveyer 12 to any suitablepoint ready for the beating machines, will contain a minimum amount ofwater. Preferably the water is warmed to a temperature of 100 to 110 F.,so as-to keep the pulp soft and pliant, and assist the solubil-' ity ofthe soda.

If desired, the degree of compression to which the pulp is subjected bythe rollers 11-11 may exceed the pressure exerted by the first set ,ofrollers 77'.. As 'a matter of practice, "the pulp will usually leave therollers 7 7 carrying only about 45%. by

weightof moisture, and when it leaves the second setof rollers, itusually carries only about 40% or less of moisture.

The saturation of the fibers is facilitated by reason of the water beingdelivered thereon'while the fibers are in a state of compression; .thenatural expansion of the fibers drawing the water into the cells so thatthe water Will permeate the fibers throughout.

From this it will be seen that the fibers will be saturated whendelivered between the rolls 11-11; the fresh water absorbed by thefibers in turn absorbing and mixing with liquors will 'be removedtherefrom. The

liquors removed from the fibers by the rollers 11-11' pass to the tank 9and mingle with the liquor delivered from the rollers 7-7'. By thusfeeding the water on the fiberin an amount corresponding to theabsorptive power of the fiber, a minimum of wash water will be used,thereby insuring no excessive liquor being delivered to the evaporator.If the fibrous, mass is not sufficiently cleansed on leaving the rollersl111, it may be delivered to a third set of rollers (not shown) and morewater added thereto, which operation may-be re peated to any desiredextent. 4

The chemical-containing liquor in the tank 9 is discharged ontoa screen14, which acts to separate such fine particles of the fibers as may beheld in the liquor therefrom; the strained liquor-being then deliveredto an evaporator B of any suitable description, by means of a pump C, orother arrangement.

The fine particles of fiber collected on th screen 14 are removedtherefrom by means of a series of wipers 15 mounted on an endless belt16, which wipers are carried across the screen. 14 continuously'by theoperation of the belt 16, in such manner as to pick up I the fibers anddeposit them on the belt 3, so

that they will be again delivered to the pressing rollers'7 7; thewipers 15 also acting to keep the screen 14 clean.v In this manner,practically all the fiber is saved, which, in conjunction with thedisintegrating action of the corrugated rolls 7-7' and 11-11' on thecoarser' fibers, obviates waste.

From the foregoing it will be seen that I have produced .a process forextracting the chemical-containing liquor from digested fibers, which israpid and thorough,- in which there is no waste of fiberor unnecessaryliquor to evaporate in the evaporator, and in which practically all ofthe chemicals can be restored; practice showing that 98 of the causticsoda is recovered by the use of my process. By this arrangement all thedigested pulp, thoroughly cleaned and disintegrated, is delivered to thebeating machines with a minimum amount of water; and the chemicals arecapable of treatment for reuse with a minimum amount of dilution.

Having thus described my invention, what I claim and desire to secure byLetters Patent is- 1. The process for treating digested fibrousmaterials to remove chemical containing liquors therefrom, consisting ofsubjecting the fibers to a combined compressing and disintegratingaction, spraying water on the compressed fibers at the moment they startto expand after their release from pressure, and then recompressing themto remove the water.

2. The process for treating digested fibrous materials to removechemical containing liquors therefrom, consisting of subjecting thefibers to a combined compressing and disintegrating action, sprayingwater on the compressed fibers at the moment they start to expand aftertheir release from pressure, 'in a quantity corresponding to theabsorptive power of the fibers, and then recompressmg them to remove thewater.

3. The method of treating wood pulp, which consists in subjecting it toa digesting process in the presence of the' soda solution, then passingit through disintegrating rollers to dislntegrate the pulp and remove apart of the soda solution, then sprayin the pulp with water, passingthis sprayed pulp through other rolls under pressure, and then treatingthe liquids thus extracted successively in an evaporator and incineratorto recover the soda values.

4. In an apparatus for treating pulp, the combination with a digester,of successively arranged pulp disintegrators, each disintegratorcomprising coactin corrugated pressure rolls, means b whic the digestedpulp is fed successivey to the rolls, and means by which the pulp issubjected to a clelansing spray after leaving each set of rol s.

5. In an apparatus for treating pulp, the combination with a digester,of successively arranged pulp disintegrators, each disintegratorcomprising coacting, corrugated pressure rolls, means by which thedigested pulp is fed successively to the rolls, means by which the pulpis subjected to a cleansing spray after leaving each set of rolls, atank for collecting the liquid extracted by the rolls, and means bywhich the pulp fibers carried into the tank are collected andredelivered to the pressure rolls.

In testimony whereof I have hereunto set my hand in the presence of twosubscribing witnesses.

BARNABAS T. NASE.

